just picked up a 1990 e250 extended van. the heater motor does not work. there is no voltage at the fan speed switch. all fuses that I can find are good. purchased a chiltons manual for wiring diagrams. It seems to have everything except whats in the dash. What a waste of my money. I'm pretty good at following diagrams and troubleshooting but don't know where to start.Is the fan switch supplying grounds instead of voltage or is the problem before the switch? If someone could post a diagram or just walk me thru the circuit I would greatly appreciate it. I could just install a toggle switch and home made harness but would rather fix it correctly. Thanks.

When you set the ac/heater selector to a position other than off it triggers the blower motor relay, from the relay a orange/red wire supplies 12volts to the blower motor, from the motor a orange/black wire carries the voltage to the fan switch, a heater resistor supplies varying levels of ground to get different speeds.

If the heater fan works on high and no other speeds it is a bad resistor, if it doesn't work at all it could be any of the 3 parts failed.If you are not getting any voltage on the orange/black wire with the selector switch set to an on position and key on you may have a bad motor.

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